Mapping of cloned human genes is performed in this laboratory by three complementary methods including Southern analysis of DNAs from a panel of well-characterized human-rodent somatic cell hybrids, in situ hybridization of metaphase spreads with biotinylated DNA probes, and genetic linkage analysis in the 40 large C.E.P.H. pedigrees. During the past year, about 15 additional genes have been chromosomally localized using the panel of somatic cell hybrid DNAs . Four genes were also regionally localized by in situ hybridization and another four genes by genetic linkage analysis. Two functional genes (NM23Hl and NM23kH2) in a multigene family of tumor suppressor genes were found to be tandemly linked (head to tail) on chromosome 17q2l-q22 and closely linked to a cluster of genes (HOX2, NGFR, and COLlAl) which are known to be physically linked within a one megabase region. Surprisingly, a sequence which cross-hybridizes strongly with the NM23Hl probe is located on a different chromosome (i.e. 16). Ordered linkage maps of genes on 14qll-ql2, 22qll.2-ql2, and 17q2l-q22 have been constructed from our linkage data. An (AAT)17 trinucleotide repeat sequence within the first intron of the interleukin 2 receptor -chain gene (IL2RB) has been used for genetic linkage analysis of IL2RB by sequencing gel size analysis of this highly polymorphic sequence after PCR amplification using oligonucleotide primers flanking this sequence. IL2RB has served as an anchor locus to order five genes on this region of chromosome 22 as well as several flanking anonymous DNA markers and genes. More importantly, in collaboration with R. Eldridge and D. Parry, the polymorphic trinucleotide repeat and a (TG)26 dinucleotide repeat in the 5' untranslated region of IL2RB were used to localize the NF2 (neurofibromatosis 2) gene on chromosome 22 in a 3-generation family segregating this gene. Additional studies are in progress to further localize this gene. A group of 35 plaques containing a trinucleotide repeat have been isolated from a chromosome 22 library and they are being used to construct a high resolution genetic linkage map and physical map of chromosome 22.